A lead free solder is a lead (Pb) free conducting material for bonding electronic components, lead being a substance that is harmful to humans.
Due to increasing environmental concerns, legal restrictions in using lead are growing stricter all over the world. In order to confront such legal restriction, recently, development of lead free solders as alternatives to lead solders has been vigorously carried out.
As an example of a lead free solder, there are Sn—Ag—Cu based solders. Among Sn—Ag—Cu based solders, a representative lead free solder having a Sn-3Ag-0.5Cu composition has a high melting point in a range from approximately 217 to 219° C., which means that soldering should be carried out at high temperature, which can lead to heat damage being caused to electronic components.